Speaker throw question

[AnotherScott]

My age old understanding of PA speakers is that the horns function like cupping your hands over your mouth when you're calling to someone at a distance... you're taking energy that would normally disperse almost equally in all forward directions, and focusing it to reach further in a particular direction, at the expense of "off axis" volume. So it is a "redirection" of the same total amount of acoustic output, which should maximize throw in the desired direction. But something about this analogy appears to be wrong, or at least incomplete, because "flat front" (non-horn) drivers actually often seem to throw *farther* than the typical PA. Guitar amps, Spacestation, line arrays (a la Bose) all seem to reach further (not fall off as quickly) compared to the horn loaded PA cabs. Can anyone explain what I'm missing here?

[Stokely]

Can't help but I have some interest in this.

My band all runs direct so in our case it's all about the PA.  We have two:  an EV evolve based one (that we use almost all the time) and a larger QSC one with subs and k10.2s on top.  I have always heard that if we needed more "throw" distance we'd use the traditional speakers, while the EVs provide less throw but much wider dispersal.   Granted there is less overall power involved with the EVs so that is a factor.     Sounds plausible to me but my amateur engineering knowledge stops at studio mixing.

Almost all our gigs that don't use sound companies are in oddball/wide spaces that aren't all that deep, and/or have strict volume requirements, and this is why the EVs get the call almost all the time.

[KuruPrionz]

LOTS of variables!!! Horn loaded systems are an older design, generally speaking. The Bose arrays are newer designs and running buttloads of small full range speakers will provide far more dispersion without compromising the energy in any particular direction. 

 

Crossover point is another, HUGE difference between crossing over at 800hz and 1600hz. Human hearing picks up way more 800hz at the same volume. 

 

Type of speaker is yet another. What is true for one type of system does not hold true for all of them. The initial attack is different (piezo drivers have a fast, harsh attack, ribbon tweeters sound smoother and less jarring. Other drivers fall in the middle somewhere. 

 

Woofer size matters, a 15" woofer will pump out more and lower bass response than a 12", 10" or 8" woofer and the bass frequencies are much less directional. That said, the 15" will "beam" higher frequencies with much less dispersion. In general, the smaller the woofer the more high frequency dispersion it will have. Which is why I favor 10" speakers for guitar amps, they spread the sound better than a 12" or 15" speaker. 

 

I'm sure there's more, this topic could be a complete 6 month course at Uni, somebody probably teaches it somewhere. Not saying I got an A, I just learned a few relatively simple details out on the gigs. 

Hopefully somebody chimes in that knows more than I do!!! 😁

[stoken6]

14 hours ago, AnotherScott said:

Guitar amps, Spacestation, line arrays (a la Bose) all seem to reach further (not fall off as quickly) compared to the horn loaded PA cabs

Line arrays have very different dispersion characteristics with less vertical dispersion and less fall-off as distance increases. The speaker-design specialists will talk about "coupling" and the like - I satisfy myself with the following highly unscientific explanations:

 

If you're close to a line array, then you're listening to one speaker, as most of the other speakers in the array go straight past your ear. As you move away from the array, the perceived volume of that one speaker drops of course, but it is compensated by the fact that you can "hear" a greater number of speakers. 

 

As I say, highly unscientific, and easy to pick holes in, but it helps me sleep at night...

 

Cheers, Mike.

[Tusker]

Stoken, I love your explanation of one versus multiple speakers. I get that. 🙏

 

But you also mentioned that line arrays have less vertical dispersion and that’s a head scratcher for me.  Is that because of driver size or vertical positioning or something else? 😅

[AnotherScott]

17 minutes ago, Tusker said:

you also mentioned that line arrays have less vertical dispersion and that’s a head scratcher for me.  Is that because of driver size or vertical positioning or something else? 😅

 

As a variation of the D'Appolito concept, I think maybe that the tower of identical drivers limits the vertical dispersion of each "middle" driver by interfering with the dispersion of the driver immediately above and/or below.

[AnotherScott]

Expounding on my initial post... I intentionally compared the horn based PA cabs to a variety of different  non-horn designs (single "flat" front-facing guitar amp, Spacestation front+side, Bose-style line array). Since I thought the design of the horn is supposed to increase throw distance by reducing dispersion, it seems odd to me that--unless I'm mistaken--I think these different non-horn designs all throw further! That is, they drop off less with distance compared to the horn. And since I thought one of the main benefits of a horn was to increase throw distance, I'm wondering what I'm missing.

 

A plain guitar amp, despite having no horn, actually seems to carry quite far, and is, in fact, very directional (i.e. if the amp is on the floor of the stage, you will hear much more of it if you crouch down than if you're standing up, which is why guitarists so often put their amp on a stand). I know, high frequencies by their nature are more directional, but it is not just that the sound's "brightness" changes substantially depending on how close the amp is to your ear level, the volume of the full body of the sound changes dramatically. So it is, for whatever reason, highly directional despite not having a horn to "direct" its sound, and has the long throw that I am (rightly or wrongly) associating with high directionality. But the Bose line array has different directional characteristics (very wide, but not very high), and also long throw. And the spacestation, by virtue of its phase manipulations, has almost no identifiable directionality (once you get out of its immediate distance) and again a long throw. Numerous scenarios, though none of them, I believe, throw less than a horn based PA speaker... they actually seem to throw more. So there is a lot here that is counter to what had been my understanding about horns.

 

[Irena]

I'm no expert on this topic either, but I'd add overall enclosure design to the big list of variables as well--e.g., ports, and even cabinet material. Maybe it's also worth noting that the original impetus for compression horn drivers wasn't so much to direct sound as it was to improve efficiency back in the days that amplification power was heavy and expensive. I don't really know the physics of how a compression driver achieves close to 10X efficiency over a flush-mounted cone, but as someone smart once explained it to me, a driver's ability to make noise at a given input wattage increases with air density in the same way that a canoe paddle delivers more power when pulled through water than when pulled through air.  Building on that idea, the narrow throat of a compression driver impedes the air from dissipating as quickly as it would in a surface mounted design (i.e., making the air "thicker" close to the driver), and the driver ends up producing a higher SPL at a given wattage. (Maybe someone with a strong technical understanding can weigh in with a better explanation... )  The widening duct beyond the throat allows sound to be radiated more broadly for sound reinforcement applications.  That efficiency comes with some tradeoffs of course, and the lightweight Class D amps we have now have made it more viable to throw thousands of watts at other, less-efficient options.

[Al Quinn]

I’ve noticed that the Motion Sound KP-610S provides a bigger sound, which I associate with more throw, than a pair of RCF TT08As. I reached this conclusion by using each on different days at the same venue with the same band. It’s my understanding that the TT08A uses a horn while the KP-610S uses “flat front” drivers for the highs. I think my observation supports what Scott is saying but, unfortunately, I don’t have a technical explanation for this. 

[elif]

The short answer is that the "throw" of the horn depends on the geometry of the horn that is loading the driver.  Whether of a constant-directivity type, exponential, conical, or some computer designed thing in between, they all take the total acoustical power of the driver and disperse it in some defined pattern. I once bought a Renkus-Heinz constant directivity horn, bolted it up to a driver and measured its on-axis response.  Because the response of the driver was flat, I was expecting the response of the horn & driver to be flat with frequency.  It was not.  In fact, the response reduced as the frequency increased.  I thought something was dreadfully wrong until I realized that because it was a constant-directivity type, the acoustical power was distributed to create the constant-directivity pattern.  There was a fall off in response, but the fall off was the same off-axis as on.  An exponential horn response would have been flat on-axis but would have fallen quickly off-axis.  BTW, the fall-off in response with frequency was easily compensated by EQ.

 

I guess that wasn't a short answer after all.  😜